1. Field of the Invention
The present invention relates to a gelled negative electrode for an alkaline battery containing a gelling agent polymerized in a non-benzene solvent and an alkaline battery using it as a negative electrode.
2. Description of Related Art
In general, a gelled negative electrode, which is obtained by gelling a mixture of alkaline electrolyte and zinc powder with an gelling agent added, is used as a negative electrode of an alkaline battery. As the main component of the gelling agent, a cross-linked poly(meth)acrylic acid (or salt) formed by polymerizing a (meth)acrylic acid (or salt) is used in general, wherein the gelled negative electrode is adjusted to have a predetermined viscosity for preventing the zinc powder from sedimenting in the alkaline electrolyte.
When the added amount of the gelling agent is increased, the internal resistance of the battery increases to degrade the discharge characteristics of the battery. When the added amount of the gelling agent is reduced in contrast, sedimentation of the zinc powder is suppressed insufficiently to degrade the discharge characteristics of the battery and to shorten the lifetime thereof.
To tackle these problems, Japanese Unexamined Patent Application Publication 2003-123763 proposes a technique for enhancing the thickening effect of the gelling agent by adding ultra-fine particles of a metal oxide to the gelling agent. This reduces the added amount of the gelling agent required for attaining the predetermined viscosity and prevents degradation of the discharge characteristics caused due to an increase in internal resistance of the battery.
Japanese Unexamined Patent Application Publication 2000-306589 discloses a technique for forming a gelling agent made of a cross-linked poly(meth)acrylic acid (or salt) having a large particle diameter by aqueous solution polymerization or reverse phase suspension polymerization. This suppresses sedimentation of the zinc powder to prevent degradation of the discharge characteristics and shortening of the lifetime of the battery.